Vehicle restraints are utilized to increase safety at a loading dock. The restraints secure a truck trailer to the loading dock structure or building when goods are transferred between the trailer and the building. The restraints typically engage a rear horizontal bar referred to as the Rear Impact Guard (RIG) or ICC bar. The ICC bar is located at the rear end of the trailer below the trailer bed. When the trailer is backed up to an available loading dock stall, the ICC bar is positioned close to the face wall of the dock. Bumpers typically extend from the face wall to protect the trailer, dock and any dock leveling fixture at the dock. The restraint helps avoid accidents by securing the trailer to the loading dock so that the truck driver does not inadvertently pull the trailer away when it is being loaded or unloaded. Trailer restraints typically include a hooking device located in front of the dock and anchored to the dock or ground. When in use, the hooking device places a barrier in front of the ICC bar to secure the trailer so that it cannot move away from the dock.
Conventional trailer restraints include storable restraints and impact restraints. Storable restraints move between a raised operating position and a lower stored position. When in the stored position, a trailer should clear the device as it is being backed into an available loading dock stall. Conventional storable restraints are disclosed in U.S. Pat. Nos. 4,488,325, 5,096,359 and 4,964,777. When the trailer and dock leveler are properly positioned with the lip of the leveler resting on the trailer bed, the stored restraint is activated to rise up and securely engage the RIG. Restraint mechanisms of this style are powered into their raised position by motors, springs, or other mechanical means.
Impact restraints include a movable carriage that adjusts to the height of the trailer RIG. The incoming RIG engages a sloped portion of a carriage, which pushes the carriage down and into aligned engagement with the RIG as disclosed in U.S. Pat. Nos. 4,264,259 and 4,560,315. The carriage has a motor that rotates a hook from a release position to a securing or locking position. An operator actuates the motor when the RIG is engaged with and aligned over the carriage. The rotation of the hook causes it to emerge from the carriage and securely engage the RIG.
One problem with storable trailer restraints is their complexity and inefficiency. These problems result from the need for a low stored position, a large range of extension and a uniform upward force to lift the barrier. When in its stored position, the restraint must be low enough to avoid unintended impact or collision with a wide variety of trailers and ICC bars, even when the trailers are heavily loaded and riding low. Given the force of the truck and weight of the trailer, unintended impact by the trailer or ICC bar with the restraint can severely damage the restraint. During operation, the restraint must rise sufficiently high to engage a wide variety of trailers and ICC bars, even when the trailers are empty and riding high. Failing to properly engage the ICC bar can result in serious injury to loading dock workers and even loss of life. For efficiency and safety reasons, the barrier should be raised with a substantially uniform upward force. If the upward lifting force is too small during any portion of the raising movement, the barrier will stall and fail to engage, or fail to stay engaged to the ICC bar. Excessive upward lifting force is inefficient making it difficult for the dock worker to store a manually operated restraint. Conventional designs are overly complex in their attempt to achieve a low stored position and a wide range of vertical barrier movement, while applying a uniform upward force to the barrier. Their bulky designs and heavy weight, which can require lifting the motor itself, are particularly inefficient.
Another problem with conventional loading dock trailer restraints is durability. This problem is of particular concern for impact type restraints. Impact restraints are subject to damage from trailers that are out of square when they are being backed into the docking stall. The trailer and ICC bar can exert tremendous force when they impact the carriage that can twist the entire mechanism. As a result, these restraints are typically bulky, which leads to increased cost of materials and repairs.
A further problem with trailer restraints is their harsh working environment. Storable and impact type restraints are mounted outside on or near the ground where dirt, debris, snow, ice, rain, humidity and temperature all contribute to the wear and tear on the device. The component parts of the restraints deteriorate over time, which causes binding and even the failure of the device. An impact style restraint or a trailer can be damaged when the ICC bar impacts a binding or frozen carriage and attempts to force it down. Solid debris such as rocks, wood or metal can collect beneath an impact type restraint when it is in use, which interferes with the proper movement of the carriage. In addition, attempts to protect moving parts and any sensors via a separate outer housing have been largely unsuccessful. Impact restraints require the hook to extend from the housing, the performance of which can be impaired by the harsh environment.
A still further problem with conventional trailer restraints is false signals that incorrectly indicate the status of the restraint or ICC bar. Binding of sensing component can lead to false signals such as the position of the restraint. Sensing devices near the throat of the hook can also become contaminated or damaged, leading to false signals, such as whether the ICC bar is engaged or disengaged. These false signals can lead to frustration, damage to the restraint or trailer, and serious injury to loading dock workers.
A still further problem with conventional trailer restraints is maintenance. Component parts should be configured to allow easy access and servicing. For example, many storable restraints have guide tracks that turn inwardly to form a central U-shaped compartment for receiving the main guide rollers for the barrier. This compartment collects dirt, debris and ice that is difficult to clean out. The rollers are also difficult to inspect and service. Yet, the contamination of the track and rollers causes increased friction, binding and eventually sustained damage.
A still further problem with conventional trailer restraints is pullout strength. The restraint must be able to prevent a truck from inadvertently pulling a trailer away from the loading dock.
The present invention is intended to solve these and other problems.